This invention generally relates to fault monitoring and diagnostic control circuitry for telephone switching systems and more specifically to fault monitoring and diagnostic control circuitry that includes test calling circuitry.
Early mechanical telephone switching systems incorporated essentially no fault monitoring and diagnostic controls. Faults were generally detected when a telephone line faulted. Then maintenance personnel set out to locate the fault and repair it.
More recently, however, telephone switching systems have become more sophisticated. They incorporate digital data processing equipment as control elements. The analog signals now are converted into binary form for switching purposes, and the binary signals then are converted back to analog form.
At least some of these systems include some form of automatic fault monitoring and diagnostic control circuitry. More specifically, in one such system two independent telephone switching circuits are cross coupled. One circuit performs the actual telephone switching while the second circuit monitors operations in the one circuit. If a fault is detected, the second circuit provides the actual switching while the first assumes the role of the fault monitor. Telephone switching systems of this type are characterized by using large, expensive specially designated data processing equipment.
It is an object of this invention, to provide an automatic test call generator for a fault monitoring and diagnostic control system for a telephone switching system.